Heater



FIG. 1 is a front view of the design for a heater in accordance with the present invention;

FIG. 2 is a view of one side thereof;

FIG. 3 is a view of another side thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof. 

The ornamental design for a heater, as shown. 